In the bone marrow and basal lamina in the body, cells grow and proliferate in an extracellular matrix constituted of a fiber-like structure of a nano level such as collagen and the like. To provide cells necessary for cell medicine and regenerative medicine, a scaffold material for cell culture that enables efficient culture of cells ex vivo is desired. It is preferable that such cell culture scaffold material mimic as much as possible the in vivo environment surrounding the cell.
It has conventionally been studied to process matrix constituent materials such as collagen and the like extracted from the body into a gel or sponge-like structure and use same as a culture scaffold when cells are cultured ex vivo (see patent document 1). However, these substances derived from living organisms and mainly composed of protein are associated with problems of inability to stand sterilization treatments with autoclave, γ-ray and the like, stability during long-term preservation before use, physical strength, form stability and the like. In addition, since these substances derived from living organisms such as collagen and the like are generally extracted from animals such as cow, pig and the like, a risk of introduction of an infectious substance from these animals is present.
Therefore, studies of structures such as foam, gel, fiber and the like produced using synthetic polymers as materials instead of substances extracted from living organisms, which are used as a culture scaffold, are recently ongoing (see patent document 2-patent document 5). Particularly, application of a synthetic polymer including N-hydroxysuccinimide (NHS) acrylate ester monomer, hydrophilic monomer, and a crosslinking agent to a surface of a cell culture substrate is disclosed (see patent document 6).
Of these, a structure constituted of a nanofiber having a fiber diameter of a nano level, which is formed by an electrospinning method (electrospinning) including blowing the fiber by applying a high voltage, is drawing attention as a cell culture scaffold material. Many attempts have been made to culture, on the nanofiber, functional cells and pluripotent stem cells, which are used for cell medicine and regenerative medicine, while maintaining an undifferentiated state (see non-patent document 1-non-patent document 3). However, it is difficult to impart cell adhesiveness and proliferability to such fibers derived from synthetic polymers, and they cannot be said to mimic the in vivo environment.
To improve this aspect, a nanofiber immobilizing a cell adhesive peptide containing RGD has also been studied (see non-patent document 4). In this case, cell adhesive peptide is immobilized on a synthetic polymer containing an active ester group such as N-hydroxysuccinimide (NHS) ester, for which a copolymer in consideration of hydrophilicity and hydrophobicity is used to prevent dissolution of the polymer in water. This in turn limits the amount of NHS to be introduced, the amount of an immobilizable cell adhesion substances, and consequently, the cell adhesiveness of a cell culture scaffold material.